1. Field of the Invention
The present invention relates generally to an image forming apparatus, an image forming method, and a computer-readable storage medium.
2. Description of the Related Art
Liquid-droplet-ejecting image forming apparatuses that form an image by ejecting droplets of liquid such as ink onto a recording medium such as a media sheet, on which an image is to be formed, have emerged recently.
Such a liquid-droplet-ejecting image forming apparatus is capable of direct, contactless printing without requiring development, fixing, and the like processes, and therefore capable of high-speed, low-noise, high-image-quality color printing on not only ordinary paper but also on various types of recording media. For this reason, liquid-droplet-ejecting image forming apparatuses have been proliferated.
Emerging are liquid-ejecting image forming apparatuses especially of a type that attains higher image recording speed by causing a carriage including thereon a recording head that ejects a liquid droplet to reciprocate, and an image is recorded during both of forward and backward traveling of the carriage rather than only during traveling in a single direction. For the sake of clarity, it is assumed in the description below that ink is used as the liquid. Liquid droplets are referred to as ink droplets; a liquid-ejecting image forming apparatus is referred to as an inkjet image forming apparatus or the like.
Meanwhile, the viscosity of ink to be ejected changes with temperature such that the higher the temperature, the lower the viscosity.
When the viscosity of ink to be ejected from an inkjet image forming apparatus decreases, an amplitude of ink meniscus (convex or concave surface of the ink caused by interaction between a surface of a container and the ink) increases, and anomalous ejection (ink distortion) occurs.
Against this backdrop, an inkjet recording apparatus including a nozzle opening, a pressure generating chamber, an inkjet recording head, and a driving-signal generating unit is disclosed in Japanese Laid-open Patent Application No. H9-52360. The pressure generating chamber has a Helmholtz resonant frequency of a period and communicates with a common ink chamber via an ink supply port. The ink-jet recording head has a piezoelectric vibrator that expands and contracts the pressure generating chamber. The driving-signal generating unit outputs a first signal for expanding the pressure generating chamber, a second signal for causing an ink droplet to be ejected through the nozzle opening by contracting the pressure generating chamber from an expanded state, and a third signal to be output when vibration of a meniscus generated after the ink droplet is ejected travels toward the nozzle opening.
More specifically, this conventional technique adjusts an amount, by which the meniscus is to be pulled, according to the temperature, so that a resistance in an ink channel extending to the nozzle opening is cancelled out by the viscosity of the ink, and the volume of the ink droplet and a flying velocity, at which the ink droplet flies through the air, are held constant.
As described above, the conventional technique adjusts the amount, by which the meniscus is to be pulled, according to the temperature, so that the resistance in the ink channel extending to the nozzle opening is canceled out by the viscosity of the ink, and the volume of the ink droplet and the flying velocity of the ink droplet are held constant. However, in this technique, an ink droplet flies in a high-temperature condition at the same velocity as that in a low-temperature condition. Accordingly, there arises a problem in the high temperature condition where the ink viscosity decreases that anomalous ejection (nozzle distortion) occurs, which results in degradation in image quality.
Therefore, there is a need for providing a technique that allows forming a high-quality image by reducing distortion of liquid ejection in a high-temperature condition.